We did this on a whim, and were very pleasantly surprised. Captain Bud took great care of us, and we saw dozens of dolphins. We have done Dolphin trips all over the Caribbean and didn't know what to expect for Galveston. It was an awesome tour and just the right amount of time. I don't believe you can do advanced purchases except for that day, so make sure you give yourself plenty of time and get the tickets the morning you plan to go.